This invention relates generally to correlator circuits and more specifically to a novel low offset correlator circuit for adaptive processors.
Adaptive processors, whether functioning with antenna arrays, acoustical sensors or in other systems require very low offset correlators in order to form appropriate nulls upon the insertion of interference signals into the system. An offset is a direct voltage in the correlator which appears as an additional signal and has the effect of diminishing the nulling performance of the system. Conventional and known correlators have offsets which are input power dependent, temperature dependent, and power supply dependent. The instant invention substantially reduces the input power dependency, essentially eliminates temperature dependency, and completely eliminates power supply dependence.
When adaptive processors are utilized with antenna systems it is important that the correlator produce no output whenever either of the two terms to be multiplied is zero or whenever the terms are in phase quadrature. Some prior art low offset correlator designs resulted in much improved performance on one hand, however, suffered either from reduced performance due to the higher signal levels necessary, higher frequencies or difficulty in obtaining well matched field effect transistor (FET) devices.
The circuit disclosed hereinafter eliminates or alleviates these disadvantages of the prior art.